Qt4 designer SLOW - how to fix?

[hvengel]

I have started porting my Qt3 app to Qt4. This of course means that I need to spend time in designer cleaning up the mess that is created when the forms are converted. (Why does this make horizontal spacers vertical? And why doesn't it just keep the same size policy settings as the Qt3 form?) I am finding Qt designer to be VERY SLOW on my system. On complex dialogs it can take 30 seconds just to select a widget and it uses huge amounts of CPU while this is happening. This can't be right and there must be something wrong with how this is configured or some other issue. Designer is so slow that it is painful to work with and this is having a significant impact on my productivity and is delaying the porting work that I need to do. Anyone here have any ideas about how to fix this?

[wysota]

Remember that automatic gizmos might sometimes fail. For some dialogs it might be easier to simply recreate the form in Qt4 Designer instead of relying on Designer to port them by itself. Why did it wreck your form? I don't know, I'd have to see the Qt3 form and try it myself. Why is it slow? Probably either because of an incorrect port, an unstable version of Designer or because of a big complexity of the form in question.

[hvengel]

The forms were ported using uic3 -convert. I have most of the issues related to the conversion sorted out but things are still running very slow. Designer eats up CPU when I do anything in it and running top I see that this is in calls to xorg. Even on very simple forms it is slow as in taking 5 seconds to select a widget.

But I did some googling and it appears that there are problems with Qt4, XRender and the Nvidia proprietary drivers. I found one source that says to set QT_X11_NO_XRENDER=1 and I found that designer is now very fast but it has a negative impact on the look of Qt4 apps. For example buttons no longer have a border. But this I can live with since the performance the other way was so bad that it was making me wish I had not started work on the Qt4 port.

[wysota]

You might want to inspect the generated code manually (again, tools are not perfect) and make sure you run the stable version of Designer (meaning no 4.4 snapshots or tp1).